Ohm meters – Buying guide and Comparison
If you are only interested in finding a good milliohm meter to take readings from low resistance wiring with a high degree of accuracy, then we recommend you check out the Amprobe MO-100. This highly specialized product will most certainly fit the requirements of any professional or dedicated hobbyist. Its resolution of only 100 microhms allows for an extreme degree of precision when diagnosing low resistance installations, and the maximum range of 2000 ohms will make it useful for testing a wide variety of electrical equipment employed in the automotive, industrial and HVAC fields. Like any high-end ohmmeter should, it’s outfitted with four input terminals, to allow for the extra degree of accuracy that four-wire resistance measurements provide but it also has a couple of interesting, unique features to place it above the competition. If the MO-100 doesn’t agree with your budget, a more basic but equally high performing unit is the Extech 38056.
Finding the best ohm meter can be hard since the items you’ll be looking at, tend to vary quite a lot in regards to what specific type of task they are intended to do. They all measure electrical resistance, apparently, but the actual application they are best suited for can be very narrowly defined. We hope that the following guide will help give some pointers as to what type of ohm meter will best fit your specific needs.
Types of ohm meters
There are three main types of tools we can refer to as an ohm meter: milliohm meters, generally used to measure the resistance of all varieties of couplings and conductors; megohmmeters which test insulations; and the versatile digital multimeter, which offers a wider degree of functionality but generally works with ranges closer to the megohmmeter.
Since the purpose of the milliohm meter is to provide readings in places that are supposed to have a high degree of electrical conductivity, its ranges for measurement start very low — as low as a hundred-millionths of an ohm — and rarely reach more than a couple of thousand ohms, which is often enough even for the most underperforming coupling.
Their degree of sensitivity should be very high to ensure adequate performance, and due to the added cost this entails, they are most commonly found in professional settings, or as a niche investment from dedicated hobbyists and handymen. A milliohm meter can be very useful if you want to ensure that electrical units around the housework at peak efficiency, or for diagnosing shorts in motors or electrical wiring, but most home users generally look towards the higher versatility of a multi measuring tool for everyday needs.
Nearly all clamp meters or digital multimeters available for sale today come with a resistance measuring function. But even the best digital volt and ohm meters won’t provide the same degree of accuracy as more specialized tools. Their ranges can vary from the milliohms right into the megaohms, but you’ll rarely get such versatility from a single item. More expensive units can be specialized to work well with lower resistances, but most generally stick to only providing accurate measurements for insulation material due to the lower resolution required.
Megohmmeters are specialized in testing the state of insulating material used in a wide variety of places that include but are not limited to motor windings; refrigerator compressor; washing machines; panel boards and relay control circuits. Obviously, these are a somewhat useful tool to have around the house, since faulty insulation on various appliances can prove a substantial fire hazard. Their ranges can go as high as 1000 megaohms (basically 1 billion ohms), but you’ll rarely get to use that unless working in a nuclear power plant.
Other things to look out for
Added features that will improve our experience when using the product should be taken into account regardless of what type of meter we’ve settled for. A display that’s clear and easy to read, preferably backlit for outdoor use or buttons that are firm to press and dials that require significant force to turn are all things to consider in order to avoid getting small annoyances out of the product later on.
When it comes to greater annoyances and potential accidents, we should make sure that the probes are well isolated and that the unit offers some measure of protection when working with high voltage installations.
The power source is also important, since the use of a common type of battery, or the ability to plug the device into your household outlet can make for some extra welcomed convenience.
Top ohm meters reviews in 2017
Considering the most important factors to account for when shopping for each specific type of resistance testers, we’ve taken a look through the best ohm meter reviews to be found online and made a selection of our favorite units for your consideration.
As a milliohm meter, this Amprobe product is all about resolution and accuracy. To this effect, it uses four color coded input terminals that allow for extra-accurate four-wire readings. It can also deliver three different test currents to work out a mean for the closest to life result. It’s also capable of indicating whether or not connection problems or temperature might have falsified the results.
Thus, the MO-100 achieves the truly impressive resolution of just 100 microhms for its lowest operating ranges, (meaning from 200 milliohms up to 2000 milliohms) without requiring test leads resistance compensation. The range goes all the way to 2000 ohms, enough for testing certain types of plating employed in vaping apparatuses, while the resolution also increases progressively as a measure of convenience.
To prevent its highly sensitive measuring apparatus from getting damaged, this meter also gives out over-temperature and over-voltage warnings to the user.
The MO-100 is a highly sensitive machine with a minimum resolution of 100 microhms at ranges as low as 200 milliohms, enough to accurately test any electrical appliance that can be found around the house at a professional level.
The option of three different test currents allows the user to confront multiple results in order to reach the most accurate measurement.
A specialized indicator informs of whether or not connection problems or high heat might have interfered with the results.
It offers high temperature and high voltage indicators, which is a welcomed safety feature considering the delicate nature of milliohm meters.
It conforms to every international safety standard, as well as American, Australian and EU safety regulations. Its four test leads come with alligator clips for hands-free use and a shrouded plug that protects against shock.
The unit does require 1 nonstandard battery to provide adequate current or voltage when performing the test, but this is already included upon purchase.
Buy from Amazon.com for ($581.21)
This Extech model has very close specifications to the Amprobe MO-100, which by itself speaks very highly of its quality, but the designers of the 380560 seems to have favored a more restrained approach when it comes to extra features. Even the unit’s design looks conservative, reminiscent of a 70s piece of technology with a red on black display, silver casing and three LED indicators — 2 of them red and one green.
More importantly, it achieves 100 microhms of resolution at 200 milliohms of minimum range, which is only one out of seven you will have to work with. It has a built-in comparator for Hi/Lo/Go resistance testing and selection, an automatic zero function and the same 4-wire cables system as the Amprobe model, this time ending in Kelvin clip connectors.
It’s limited to only one setting of 5 V for the test voltage, but it doesn’t require any sort of special batteries to operate.
Good accuracy, in the same range as the Amprobe MO-100, with 100 microhms of minimum resolution at its lowest functioning ranges.
It employs four input terminals that allow for four-wire readings to be taken. This makes for significantly higher accuracy over the more traditional 2 wire system.
The Extech is a relatively affordable solution for a product of its class; it might be preferred by people who might not see so much use out of it, like household users or hobbyists over models that offer more features.
It’s not, however, entirely bereft of features, with a built-in comparator for Hi/Lo/Go resistance testing and an automatic zero function.
The fact that it doesn’t need special batteries to operate makes for good convenience.
Can be said to be lacking in safety or performance-enhancing features when compared to similar models, but makes up for it in cost.
Buy from Amazon.com for ($476.87)
Described by its manufacturer as an affordable alternative to taut band megohmmeters the Supco M500 promises to be a convenient tool to have whenever you need to check up on some electrical insulation around the house or workspace.
Judging by the response it received from satisfied customers on retail sites, we can conclude it largely kept to that promise. It’s been praised for its usefulness when testing gate openers by people working in the industry and for making sure that 3 phase electric motors work as they should.
With a very simple design and its information display basically consisting a dozen or so LED indicator lights this item will prove very easy to use effectively by even the most casual and relaxed of people. Just stick the two probes to the element you want to test and push the big red button!
The Supco M500 is a reliable piece of electrical equipment that can be used to measure resistances of up 1000 megohms, enough for anything a casual user might encounter around his house or workplace.
Extremely convenient and easy to operate, it lets you know the state of the tested material by employing LED lights and a simple colored scale. This also means it won’t take any time for it to be set up.
While the item can be said to be a “safety feature” all to itself, the ease with which it operates adds to its safety potential since it allows the operator to be attentive at more important things than adjusting the tool.
This item was made in the USA, which is typically an indicator of reliability and quality.
It’s obviously not as high performing as taut band megohmmeters but might prove better suited for casual users.
Buy from Amazon.com for ($83.76)
This Crenova model is your basic digital multimeter. Good for use in schools, labs, industrial settings, and households for taking all sorts of measurements of an electrical nature, which of course also includes resistance. As we’ve said previously the clearest advantage offered by multi-meters consists in their versatility. If you aren’t particularly interested in conducting factory level testing on home or work appliances but just want a handy tool to use from time to time, this device might be right for you.
It can take readings of voltage and current for both AC and DC, frequency and resistance within a range of 200 ohms to 20 megohms. The last one has a measured accuracy of +/- 0.8% +2 for the lower ranges and a little bit lower once you reach the megaohm territory.
A thing worthy of note regarding its accuracy is that one of the customer reviewers tested this little device against a Fluke unit and its readings came up very close to those of the much pricier unit.
This device has a high degree of versatility, it can be used to measure voltage, amperage, frequency as well as electrical resistance. This makes for a very good value for casual use.
When resistance is concerned, it has an acceptable range for household use. Twenty megaohms is the minimum required for most insulation material to be considered safe and this is where the Crenova stops, making it useful for “sniffing out” poor insulation.
It’s been noted that this multimeter offers a very good degree of accuracy, even when compared with well calibrated semi-professional models.
It includes some good convenience features, such as a backlit display, auto shutdown and auto ranging which further recommend it for casual, day to day use.
Most customers found the manual to be poorly translated and less than helpful. There’s an abundance of relevant guides to be found on the internet, however, so this isn’t really an issue.
Buy from Amazon.com for ($17.99)
Another convenient little multimeter for every day and semi-professional use comes from AccuWorks. The XL-830L includes everything you’d want from a DVM, meaning a voltmeter, amp meter, ohm meter and diode continuity tester. You can switch between all of those with a convenient dial, and its large, easy to read display has room enough for three easily visible figures and an indicator marking.
It’s rated for both CAT II and CAT III electrical installations of up to 600 V and has a specialized battery testing function, which adds a welcome touch of extra convenience since DVMs see most of their use testing batteries. As for its own batteries, it operates with the common 9V type.
It’s range for electrical resistance measurements only goes as far as 2 megaohms, however, which might not be enough for the more demanding but will probably prove adequate for casual users.
A very versatile piece of equipment, the fact that it can take a wide variety of measurements means that it will see a lot of use around the house or workspace.
For extra functionality, it features a continuity function, which lets the user know if a certain conductor has current running through it by emitting a low-intensity noise.
It has a decent enough construction, which employs rubber for the dial and the buttons and plastic for the case.
It’s highly portable and easy to use, the display has a specialized high light function for outdoor use. The unit also automatically shuts down after a while if not in use.
While the ranges for all its other functions are good enough, the 2 megaohm limit for resistance makes it somewhat lag behind the competition as far as ohm measuring units are concerned.
Buy from Amazon.com for ($49.99)